Distributed systems may be realized by a Service Oriented Architecture (SOA), wherein communication between web services may be realized using electronic messages (e.g. XML-based messages such as SOAP messages). Said messages may be prone to attacks. Said attacks may involve a plurality of consequences such as unauthorized access, disclosure of information, and/or identity theft. Basically, said attacks may relate to modifications of the messages, which, therefore, may be classified as rewriting attacks, and more particularly as XML rewriting attacks. In particular, said attacks may exploit a weakness of XML Signature (i.e. the W3C recommendation “XML Signature Syntax and Processing”), which may be used to sign electronic messages. Specifically, SOAP is a widely established message structure specification used for exchanging messages between web services in a SOA environment. SOAP may use the W3C XML Signature specification as a security mechanism to address proof of origin and content integrity issues of XML-based messages. The W3C XML Signature specification enables the signing of not only a whole message but also one or more sub-sets of a message, referred to as a sub-message hereinafter. Signing only a sub-message using the W3C XML Signature specification may enable security attacks (e.g. rewriting attacks) on electronic messages and may make secure message exchange vulnerable.
It should be understood that a signature defined according to the W3C XML Signature specification is referred to as an XML signature throughout the text.